GB2531489A

GB2531489A - Passive cooling system for concrete containment vessel

Info

Publication number: GB2531489A
Application number: GB1603314.4A
Authority: GB
Inventors: Lu Donghua; Wenhua Niu; guanhua Fan; Yu Li; Qinglong Wen; Xiangang Fu; Jianhua Cao; Xianghui Lu; Yonggang Shen
Original assignee: China General Nuclear Power Corp; China Nuclear Power Technology Research Institute Co Ltd
Current assignee: China General Nuclear Power Corp; China Nuclear Power Technology Research Institute Co Ltd
Priority date: 2014-07-30
Filing date: 2015-03-20
Publication date: 2016-04-20
Anticipated expiration: 2035-03-20
Also published as: CN104167231A; GB2531489B; GB201603314D0; WO2016015475A1

Abstract

Disclosed is a passive cooling system for a concrete containment vessel, comprising a water tank (120) and at least one return heat transfer system (130), the return heat transfer system (130) comprising a heat exchanger (131), a riser (132), a down-take pipe (134) and a condenser (133). The water tank (120) is provided at the top of a containment vessel (110) and the inside thereof is divided into a water-cooling descending channel (127), an air-cooling descending channel (129) and a rising channel (128) mutually communicating, the air-cooling descending channel (129) and the rising channel (128) respectively communicate with an atmospheric space, the return heat transfer system (130) passes through the containment vessel (110) in a sealed manner and is partially provided in the rising channel (128), and another part of the return heat transfer system (130) is located in the containment vessel (110). Using the return heat transfer system (130) means that the heat transfer temperature difference is small, adjustments can be automatic according to the temperature of the working medium and amount of heat in the containment vessel (110), and in the case of an incident, the temperature in the containment vessel (110) is more easily kept cool to below design limits. The system has a high degree of passive safety, has a simple structure, and is easy to maintain, takes into account the two operating conditions of water cooling and air cooling, and meets the requirements of both initial removal of most residual heat in the event of an incident and taking into account long-term cooling of the containment vessel.

Description

PASSIVE COOLING SYSTEM OF CONCRETE CONTAINMENT

FIELD OF TI-liE INVENTION

100011 The present invention relates to the field of safety equipments for reactors in a nuclear power plant and, more particularly to a passive coohng system suitable for a concrete containment.

BACKGROUND OF THE INVENTiON

100021 Nuclear reactor is equipment with nuclear fuels loaded to achieve a controllable fission chain reaction. Whilc containment served as the final protection to prevent radioactive products from releasing to the environment is important safety equipment in the reactor. Recently, the requirement to the containment is rigorous jncreaslngiy. with the safety reqwreineni to the nuclear power is progressively.

10003] The existing containment in the PWR nuclear power plant wid&y adopts a concrete structure. However, since the concrete with thick wall has poor heat conduction, thus the heat in the concrete containment can not be removed to the atmosphere by itself after an accident. In this connection, active cooling equipment is used iii some nuclear power plants to remove the residual heat from the containment, which runs by means of the external power; however it will lead serious consequences in case of in-plant power failure or other situations. Thus a passive containment cooling technique is proposed in die tin rd-generation reactor.

100041 For example, Westinghouse Electric Company LLC configured a steel shell inside the concrete containment iii the AP1000 design to efficiently remove the heat from the reactor containment. Specifically, a water tank and a water distribution system are installed on the top of the steel shell, and further an air passage for the containment is arranged. After a reactor accident, the water distribution system is turned on to make water flow downward to the top of the steel shell, thereby removing heat by means of evaporation or convection.

L0005J For a fbrther example, in a passive concrete containment residual heat removal technique designed by China, a heat exchanger is arranged inside the containment, and a water tank and a steam-water separator are arranged outside the containment. After a reactor accident, the temperature and the pressure in the containment are increased, and water in the heat exchanger is boiled up by means of heat exchange so that the water-steam mixture passes through the water-steam separator, after that, the water reflows to the water tank while the steam is released to the atmosphere.

[0006J However, in regard to the prior art of steel shell serving as a part of the cooling system in the first example, the steel shell is a pressure vessel with a large diameter, which requires high manufacturing technology, and brings problems such as corrosion after long-tenn using. In the first example, the water distribution system requires dedicated design to ensure water uniformly distributed on the surface of the shell. In regard to the prior art of passive evaporation cooling system in the second example, the system is complicated since a water-steam separator is needed; and water may not be vaporized under a temperature lower than 100°C, which causes the starting of the cooling system be slow to limit the cooling capability in early stage in an accident. Further, the system can not Temove the heat efficiently after the cooling water is evaporated to dryness.

[0007] Thus, there is a need to provide a passive cooling system for cooling down the containment at early stage and late stage of an accident, to overcome the drawback mentioned above.

SUMMARY OF THE INVENTION

[00081 One objective of the present invention is to provide a passive cooling system with simple structure to efficiently cool down concrete containment at early stage and late stage of an accident.

[0009J To achieve the above-mentioned objective, a passive concrete containment cooling system adapted to remove heat from a containment includes: a water tank adapted for being configured on a top of the containment, and the water tank being divided into a water cooling downward channel, an air cooling downward channel and an upward channel which are communicated with one another, the air cooling downward channel and the upward channel communicated with the atmosphere respectively; and at least one heat exchange loop system adapted for hermetically running through the containment, a part of the heat exchange loop system being placed in the upward channel while the rest adapted for being located in the contaimnent.

[00101 Preferably, the heat exchange loop system comprises a condenser placed in the upward channel.

[00111 Preferably, the heat exchange loop system further comprises a heat exchanger adapted for being configured in the containment, an upward pipe and a downward pipe, the upward pipe is adapted for hermetically running through the containment and has two ends communicated with upper ends of the heat exchanger and the condenser respectively, and the downward pipe is adapted for hermetically running through the containment and has two ends connected with lower ends of the heat exchanger and the condenser respectively.

[00121 Preferably, the water tank is provided with a bottom wall as well as an internal wall and an external wall that are connected to and spaced with the bottom wall, and the internal wall, the external wall and the bottom wall are enclosed to form a receiving space. In such a way. the pressure of the water tank at the top of the containment is the same with the pressure of the atmospheric environment. In such a way, the system structure is simplified since a related pressure stabilizing system is needless.

[0013] Prelèrahiy, a first baffle and a second baffle separated front each oilier are vertically configured in the receiving space ol the water tank, agap is formed bet'een a lower end of the first baffle and the botloin wall and between a lower end of die second baffle and the bottom wall respectively, die upward charnel is ibrmed between the first batik and the second baffle, the water cooling downward chamiel is formed between the first baffle and the internal wall, and the air cooling downward channel is foniied between the second baffle and the external wail.

[0014] Preferably, the water tank is further provided, with a iop plate, both the internal svall and an upper end of the first baffle are connected to the top plate, an opeming is formed between an upper end of the second baffle and the top plate whereby the upward channel is communicated with the atmosphere. Based on the configuration, the steam at a high temperature and air mixtures are raised to the upper portion of the containment and contacted with the heat exchanger in the containment and then condensed and generates heat transfer between the external surfaces of Ihe heat exchanger. The steam is condensed into water which reulows to the bottom of tile containment. While the heat is transferred to the heat exchanger to make the water there:in vaporize to eillter into the condenser along the upward pipe to transfer heat by condensing. As a result, the cooilng water in the water tank is heated and then boiled to generate steam to the atmosphere directly. Due to latent heat of vaporization is high, thus overiemperature and overpressure of IFe conttainrn eril caused by a iargesca.ie energy releasing at the early stage of the accident is well prevented.

L00151 Preferably, a gap is formed between the external wall and the top plate whereby the air cooling downward channel is communicated with the atmosphere. After the water in the water tank is evaporated completely, the condenser is exposed to the air and the air in the upper channel is heated, and the heated air is raised along the upward channel. At the same time, the air at nonnal temperature enters into the upward channel through the air cooling downward channel to form the organized natural air convection; in this way, the residual heat in the containment is finally emitted into the atmospheric environment by means of air cooling. Moreover, the containment can also be cooled for a long time by means of the air cooling mode in a condition that the cooling water in the water tank is evaporated to dryness, L00161 Preferably, the water tank is in a circular structure.

L00171 Preferably, the water tank is separated into multiple independent water pools each of which is provided with the water cooling downward channel, the air cooling downward channel, the upward channel and the heat exchange loop system. The plurality of mutually independent water pools and the plurality of heat exchange loop systems are arranged; each heat exchange loop system works independently. Even if some heat exchange loop systems are invalid, the rest can still work eflèctively, so that the reliability of the system is higher.

F00181 Preferably, the heat exchange loop system is a heat pwnp system.

F00191 Preferably, the system further includes a condensate recovery system adapted for being configured in the containment and communicated with a reactor pit in the containment.

100201 Preferably, the condensate recovery system comprises a first condensate collector adapted for being arranged on an inner wall of the containment and communicated with the reactor pit, and the location of the first condensate collector is higher than that of the reactor pit. When an accidents happens, the high-powered steam produced by heating the cooling water in the reactor pit and released from the break in the primary loop of the reactor are released to the inside of the containment, part of which is condensed on the inner wall of the containment and then collected by the first condensate collector, and reflows to the reactor pit. In such a way, the water injection to the passive reactor pit within a long period of time is realized by the first condensate collector and. As a result, the natural circulation inside the containment is realized without the external alternating current power and the water source.

L00211 Preferably, the first condensate collector is communicated with the reactor pit via a first valve.

L00221 Preferably, the first condensate collector is in a groove structure and has a side wall resting on the inner wall of the containment.

F00231 Preferably, the condensate recovery system further comprises a second condensate collector adapted for being configured in the containment, located under the heat exchange loop system and communicated with the reactor pit, and the location of the second condensate collector is higher than that of the reactor pit. When an accidents happens, the high-powered steam produced by heating the cooling water in the reactor pit and released from the break in the primary 1oop of the reactor are released to the inside of the containment, part of which is condensed on the inner wall of the containment and then collected by the first condensate collector, and reflows to the reactor pit, and most of which is condensed on the wall surface of the heat exchanger and then collected by the second condensed water collector, and reflows to the reactor pit. In such a way, the waler injection to the passive reactor pit within a long period of time is realized by the cooperation of the first condensate collector mid the second condensate collector, As a result, the natural circulation inside the containment is realized without the external alternating current power and the water source.

[0024 Prefèràhiv, the second conden sate coil ector is communicated with the reactor pit via a second valve.

[0025] Preferably, the second condensate collector is in a Vshaped structure.

100261 [n comparison with the prior art, the passive concrete containment cooling system according to the invention includes the water tank configured on the top of the containment and at least one heat exchange 1001) system. [lie water tank is divided into the water cooling downward channel, the air cooling downward channel and the upward channel which are communicated with one another, and the air cooling downward channel and the upward channel is communicated with the atmosphere respectively. The heat exchange ioop system is adapted for hermetically running through the containment; a part of the heat exchange loop system is placed iii the upward channel while the rest is located in the containment. While the system is in use, the water tank is filled with cooling water Upward evaporation flow and condensate reflow are generated in the heat exchange loop system under the actions of evaporation and condensation, and water having two states of steam and liquid is the only working mediLun in the circulation channel. Further, the heal exchange loop system passing througil the contaimnent is served as the heat removal channel, and can he adjusted depending on the temperature of the working medium and the heat eneigy in the contaminent thereby cooling dovwi the containment to tile temperature below the design limiting temperature. Whie the configuraron of the water tank assists in quickly removing the residual heat from the eontanment at the early stage of accident. After the water in the water tank is evaporated completely, the part of the heat exchange loop system that is located in the water tank is exposed to the air and then the air is heated to move up along the upward channel, to fonu the organized natural air convection. In this way, the residual heat in the containment is finally emitted into the atmospheric environment. Thus, the containment still can be cooled for a long time by means of the air cooling mode in a condition that the cooling water in the water tank is evaporated to dryness. The present system can be operated passively and safely without turning on some valves and without any other assistant equipment, thus the structure is simple and the weight is light which is convenient for maintenance.

BRIEF DESCRIPTION OF THE DRAWINGS

[00271 The accompanying drawings facilitate an understanding of the various embodiments of this invention. In such drawings: [00281 Fig. 1 is a partial schematic view of a passive concrete containment cooling system according to one embodiment of the present invention; [00291 Fig. 2 is a sectional view of passive concrete containment cooling system according to one embodiment of the present invention; [0030J Fig. 3 is an enlarged view of a water cooling mode of the passive concrete containment cooling system in Fig. 2; 100311 Fig. 4 is an enlarged view of an air cooling mode of the passive concrete containment cooling system in Fig. 2; [0032J Fig. 5 is a structure view of a third baffle of the water tank in Fig. 2; and 100331 Fig. 6 is a partial sectional view of a passive concrete containment cooling system according to another embodiment of the present invention.

DETAILED DESCRIPTION OF ILLUSTRATED EMBODIMENTS

[0034] Various preferred embodiments of the invention will now be described with reference to the figures, like reference nwnerals designate similar parts throughout the various views. The passive concrete contaimnent cooling system provided in the present invention is adapted to remove heat from the containment 110 to the atmosphere after an accident, which is dependent of natural phenomenon such as natural circulation, condensation and evaporation., etc., instead of any active equipment.

[0035] RefeiTing to Figs. 1-i, in the passive concrete containment cooling system 100 according to one embodiment of the present invention, the containment 110 is a in a hollow cylindrical structure, which has a top 111 in an arcshaped structure, A pressure vessel 112, a main pump 113 and a steam generator 114 are configured in the containment 110, and the pressure vessel 112 is connected with the steam generator 114 via the inam pump 113.

0036 The passive concrete containment cooling system 100 includes a water tank 120 and at least one heat exchange loop system 130. Specifically, the water tank 120 is localed above the top lii of the contal runent 110, and the water tank is divided into a water cooling downward channel 127, an air cooling downward channel 129 and an upward channel 128 which are communicated with one another. The air cooling downward channel 129 and the upward channel 128 are communicated with the atmosphere respectively, so that the pressures of the water tank 120 is the same with the pressures of the atmospheric environment. In such a way, the system structure is simplified without a related pressure stabilizing system, [0037] The heat exchange ioop system 130 includes a heat exchanger 131, an upward pipe 132, a condenser 133 and a downward pipe 134. Specifically, the condenser 133 is placed in the upper channel 128 of the water tank 120, the heat exchanger 131 is configured in the containment 110 and located in a position near to the top 111 of the containment 110, the upper pipe 130 is penetrated through the top Ill of the containment 110 and has two ends communicated with the upper ends of the heat exchanger 131 and the condenser 133 respectively, and the downward pipe 134 is hermetically penetrated through the containment 110 and has two ends communicated with the lower ends of the heat exchanger 131 and the condenser 133 respectively. In this way, a cooling circulation channel is formed by the heat exchanger 131, the upper pipe 132, the condenser 133 and the lower pipe 134.

L00381 Under a working condition, the water tank 120 is filled with cooling water in which the condenser 133 is immerged completely. When an accident happens in the reactor in the containment 110, the steam and other substances released from the break of the reactor enter into the containment 110, resulting in the rise in temperature and pressure in the containment 110. The steam at a high temperature and air mixtures are raised to the upper portion of the containment 110 and contacted with the heat exchanger 131 in the containment and then condensed and generates heat transfer between the external surfaces of the heat exchanger 131 * The steam is condensed into water which reflows to the bottom of the containment 110. While Ihe heat is transferred to the heat exchanger 131 to make the water therein vaporize to enter into the condenser 133 along the upward pipe 132 to transfer heat by condensing. As a result, the cooling water in the water tank 120 is heated and then boiled to generate steam to the atmosphere directly. Due to latent heat of vaporization is high, thus overtemperature and overpressure of the containment 110 caused by a large-scale energy releasing at the early stage of the accident is well prevented.

While the condensate in the condenser 133 returns to the heat exchanger 131 along the downward pipe 134 to form a natural circulation. The heat exchange loop system 130 running through the containment 110 is served as the heat removal channel. which has an excellent heat exchange capacity and a low thermal resistance; thereby the present system can work under a condition with small temperature difference. The efficiency of heat exchange is high since the temperature difference is small, thus the temperature of the containment 110 can be decreased to the ambient temperature nearly. Furthermore, the present system can he operated passively arid safely without turning on some valves and without any other assistant equipment such as external power supply, thus the structure is simple and the weight is light.

[O039 After the water in the water tank 120 is evaporated competely. the condenser 133 is exposed to the air and the air surrounding the condenser 133 is heated, and the heated air is raised along the upward channel 128 At the same tune, the air at normal temperature enters into the upward channel 128 through the air cooling downward channel 129 to fonn the organized natural air convection; in this way, the residual heat in the containment 110 is finally emitted into the atmospheric environment by means of air cooling. Moreover, the containment 110 can also be cooled for a long time by means of the air cooling mode in a condilion that the cooling water i:n the water tank 120 is evaporated to dryness, which can copy with the cooling, problem of the containment 110 in a working conclit:ion of terrible accident (such as loss of coolant accident).

100401 Additionally, the condenser 133 is ananged in the water tank 120 and placed in the cooling water, so that the heat exchanger loop system 130 is in a closed structure. Once one end of the closed structure is damaged, the other end of the closed structure is still in a good condition, so that the containment 1 0 will not he connected, and radioactive substances therein will not he released to the external environment.

[004fl Referring to Fig. I to Fig. 5. the contaimnent 110 is in a cylindrical structure, and the water tank 120 al its top ill is in a circular structure, thither, the top 111 of the containment 110 is served a.s the bottom of the water tank 120 directly, thus the cooling system 100 of the invention can he applied to the exlsttng concrete containment I [0 without making major modification to the existirg, containment 110. On the other hand, such configuration of the water tank 120 is beneficial to quickly cool down the containment 10 at early stage of accident.

[O042 As well understood, the bottom wall of the water tank 120 can be the Lop 111 of the containment, or can he configured. independently, which is well known to one skilled in the art.

100431 Specifically, the water tank 120 includes an internal wall 121, an external wail 122 and a top plate 123, the internal wall 121 and the external va1l 122 are space from each other, the upper end of the internal wail 121 is fixedly connected to the top plate 123, and a certain gap is formed between the upper end of the external wall 122 and the top plate 123. The internal wall 121, the external wall 122 and the top ill are jointly enclosed to form a receiving space which is divided into the water cooling downward channel 127, the upward channel 128 and the air cooling downward channel 129, and both tile upward channel 128 and the air cooling downward channel 129 arc communicated with the atmosphere. So, the pressure of the water tank i20 at the top of the containment 110 is the same with the pressure of the atmospheric environment.

In this way, the system structure is simplified since a related pressure stabilizing system is needless.

100441 Still referring to Fig. I to Fig. 5, the water tank 120 further includes a first baffle 124 and a second baffle 125, the first baffle 124 and the second baffle are vertically spaced in the receiving space of the water tank 120, To be.

specific, both tile first baffle 124 and the second baffle 125 are in a circular structure and spaced along the circumferentia.i direction of the water tank 120, A gap is f()I11ed between the lower elk! of the first baffle 124 and the top Iii and between the lower end of the second baffle 125 and the top 111 respectively. The tipper end of the first baffle 124 is fixedly connected to the top plate 123, and an openin I 78a is formed between the upper end of the second baffle 125 and the top plate 123. The upward channel 128 is formed between the first baffle 124 and the second baffle 125, the water cooling downward channd 127 is formed between the first baffle 124 and the internal wall 121, and the air cooling: downward channel 17.9 is formed between the second baffle 125 and the external wall 122. That is to say, the water cooling downward channel 127, the upward channel 128, and the air cooling downward channel 129 are formed in sequence along the direction from the internal wail 121 to the external wall 122.

Since the top ill of the contifinment is in an arcshaped structure with a portion protruded outwards, thus the bottom wall of the water tank 120 is tilted, which makes the positions of the water cooling down ward chamiel 127, the upper channel 128 and the air cooling downward channel 129 are tapered relative to the hottoni wall. Additionally, the upper channel 128 is communicated with the atmosphere through the opening I 2$a, and the air cooling downward. channel 129 is communicated with the atmosphere through the gap between tile external wall 122 and the. top plate 123, which causes that, the. pressure of the water tank at the top of the containment ii.O is the same with the pressure of [lie atmospheric environment. In such a way, the system structure is simplified since a related pressure stabilizing system is needless.

[0045] In this way, the condenser 133 of the heat exchange loop system i30 is arranged in the circular upper channel i28 and placed in the cooling water, so that the heal exchanger loop system 130 is in a closed struciure, Once one end of the closed structure is damaged, the other end of the closed structure is still in a good condition, so that the containment 110 vi1l not he connected, and radioactive substances tiiereiii vill not be released to the external environment.

100461 In order to improve the heal: dissipation effect of the passive concrete containment cooling system 100 according to the invention, a plurality of heat exchange loop systems 130 can be arranged. To be specific, multiple heat exchange loop systems 130 are spaced and arranged around the water tank 120, and the condenser 133 for each heat exchange loop system 130 is arranged in the upward channel 128 and placed in the cooling water.

100471 Meanwhile, in order to improve the reliability of the system, the water tank 120 can also be divided into a plurality of mutually independent water tanks 120' (see Fig. 5), each of which is correspondingly provided with a heat exchange loop system 130 The plurality of mutually independent water pools 120' and the plurality of heat exchange loop systems 130 are arranged, each heat exchange loop syslem 130 works independently. Even if sonic heal exchange loop systems 130 are invalid, the rest can still work effectively, so that the reliahihty of the system is higher.

[0048] As shown in Fig. 2 to Fig. 5 specially, the water tank 120 further includes several third baffles 126 that are arranged radially. The third baffles 126 are connected between the internal wall 121 and the external wall 122 so as to divide the water tank i20 into a plurality of independent water pools 120', each water pool 120' is provided with a first baffle 124 and a second baffle 125, wherein both sides of the first baffle 124 are connected to the two adjacent third baffles 126 respectively, and the upper end of the first baffle 124 is connected to the top plate 123. Both sides of the second baffle 125 are connected to two a4jacent third baffles 126 respectively. An opening 128a for enabling the upward channel 128 to communicate with the atmosphere is formed between the upper end of the second baffle 125 and the top plate 123. Optionally, the opening 128a can be formed through either a gap between the upper end of the second baffle and the top plate 123 or by opening a through hole on the upper end of the second baffle 125 directly, which is not limited. In this embodiment, the external wall 122 is lower than the internal wall 121, so that the gap between the external wall 122 and the top plate 123 is a passage of the air cooling downward channel 129 communicated with the atmosphere. Of course, the though hole can also be opened on the external wall 122 to enable the air cooling downward channel 129 to connect to the atmosphere, but which is not limited. In this way, even if some the heat exchange loop systems 130 are invalid, the rest can still work normally, so as to improve the reliability of the system.

[0049] Preferably, the heat exchange loop system 130 is a heat pump system, which is not limited however; it also can be other heat exchange systems which are well known to one skilled in the art.

[0050] Referring to Fig. 6, difference between the passive concrete containment cooling system 100' in the present embodiment and that in the above embodiment is that, a condensate recovery system 140 is included in this embodiment. The difference is described hereinafter, and other structures same with the above embodiment are omitted.

[00S1J In the present embodiment, the condensate recovery system 140 is configured in the containment 110 and communicated with the reactor pit 115 therein. Specifically, the condensate recovery system 140 includes a first condensate collector 141 and a second condensate collector 143, the first condensate collector 141 is arranged on the inner wall of the containment 110, the position of the first condensate collector 141 is higher than the position of the reactor pit 115, and the first condensate collector 141 is communicated with the reactor pit 115 through a first valve 142. The second condensate collector 143 is arranged in the containment 110 and located below the heat exchanger 131 and higher than the reactor pit 115, that is to say, the second condensate collector 143 is located between the heat exchanger 131 and the reactor pit 115 in the height direction, and communicated with the reactor pit 115 through a second valve 144.

L00521 Referring to Fig. 6 again, the first condensate collector 141 is arranged along the inner wall of the containment 110, and preferably is a groove structure, one side wall of the first condensate collector 141 is closely adhered to the inner wall of the containment 110, the bottom wall of the first condensate collector 141 is communicated with the reactor pit 115 through a pipeline on which the first valve 142 is provided. The side wall of the first condensate collector 141 is closely adhered to the inner wall of the containment 110, so as to collect the condensate fomied by condensation on the inner wall of the containment 110 more conveniently and effectively.

F00531 The second condensate collector 143 is in a V-shaped structure, the bottom of the second condensate collector 143 is connected to the reactor pit 115 through the second valve 144. That is to say, the second condensate collector 143 is provided with two side walls both of which are inclined, and the junction of the bottoms of the two side walls is connected to the reactor pit 115 through a pipeline on which the second valve 144 is provided. The collected condensate can be quickly injected into the reactor pit 115 through the V-shaped structure.

[0054] When an accidents happens, the high-powered steam produced by heating the cooling water in the reactor pit 115 and released from the break in the primary loop of the reactor are released to the inside of the containment 110, part of which is condensed on the inner wall of the containment 110 and then collected by the first condensate collector 141, and reflows to the reactor pit 115, and most of which is condensed on the wall surface of the heat exchanger 131 and then collected by the second condensed water collector 143, and reflows to the reactor pit 115. Tn such a way, the water injection to the passive reactor pit within a longer period of time is realized by the cooperation of the first condensate collector 141 and the second condensate collector 143. As a result, the natural circulation inside the containment 110 is realized without the external alternating current power and the water source.

[0055] The working process of the passive concrete containment cooling system 100 in the embodiment is illustrated hereinafter with reference to Fig. I to Fig. 6.

[0056] When an accident happens in the reactor; the steam and other substances released from the break enter into the containment 110, resulting in the rise of temperature and pressure in the containment 110. The steam at a high temperature and air mixtures are raised to the upper portion of the containment and contacted with the heat exchanger 131 in the containment 110 and then condensed and generates heat transfer between the external surfaces of the heat exchanger 131. The steam is condensed into water which returns to the bottom of the containment. While the heat is transferred to the heat exchanger 131 to make the water therein vaporize to enter into the condenser 133 in the water tank n hO along the upward pipe 1i2 to transfer heat by condensing. Finally, the condensate is returned to the heat exchanger 13 1 in the containment 110 so as to --, 1 [cnn the natural circulation. The heat tT1sfe1red from tile condenser 1 i3 heats the cooling water iii the water tank 120 or the water pooi 120' to make the.

cooling water boiled after a certain time to produce steam raising along the upward channel 128 and released to the environment from the opening 128a, At tile same time, the cooling: water in the water lank 120 or the water pooi 120' flows to the upward channel 128 t-hrough the water cooling downward channel 127, as shown in the arrow direction of Fig. 3. Due to high latent heat of vaporization, the heat is emitted into the atmospheric environment by means of the cooling water in the water tank 120 or the water pooi 120' at the early stage of the accident, which can well prevent overtemperature and overpressure of the containment 110 caused by a large-scale energy releasing at the early stage of the accident.

100571 After the cooling water in the water tank 120 or the water pool 120' is evaporated completely, the condenser 133 is exposed to the air and the air sunounding the condenser 133 is heated, and the heated air is raised along the upward channel 128 and released into the atmospheric environment through die opening I 28a. At the same time, the air at normal temperature enters into the air coolmg downward channel 129 through the gap between the exiernal wall 22 and the top plate 123 and flows toward the upward channel 12$ to fonn the organized natural air convecon, as shown in the arrow direction of Fig. 4; in this way, the residual heat in the containment 110 is finally emitted into die atmospheric environment by means of air coolmg to realize the emission of the large residual heat in the containment 110 at the early stage of the accident.

Moreover. the containment. 110 can also be cooled for a long time by means of the air cooling mode in a condition that the cooling water in the water tank 120 or the water pooi 120' is evaporated to dryness, which can copy with the cooling problem of the containment 110 in a working condition of terrible accident (such as loss of coolant accident).

[OO5SJ Additionally, the high-powered steam is produced in the containment 110, part of which is condensed on the inner wall of the containment 110 and then collected by the first condensate collector 141, and reflows to the reactor pit 115; and most of which is condensed on the wall surface of the heat exchanger 131 and then collected by the second condensed water collector 143, and reflows to the reactor pit 115. in such a way, the water injection to the passive reactor pit 115 within a longer period of time is realized by the cooperation of the first condensate collector 141 and the second condensate collector 143. As a result, the natural circulation inside the containment 110 is realized without the external alternating current power and the water source, as shown in Fig. 6.

F00591 The passive concrete containment cooling system 100 according to the invention includes the water tank 120 configured on the top of the containment 110 and at least one heat exchange loop system 130. The water tank is divided into the water cooling downward channel 127, the air cooling downward channel 129 and the upward channel 128 which are communicated with one another, and the air cooling downward channel 129 and the upward channel 128 is communicated with the atmosphere respectively. The heat exchange loop system 130 is adapted for hermetically running through the containment 110; a part of the heat exchange loop system 130 is placed in the upward channel while the rest is located in the containment 110. While the system is in use, the water tank 120 is filled with cooling water. Upward evaporation flow and condensate reflow are generated in the heat exchange loop system 130 under the actions of evaporation and condensation, and water having two states of steam and liquid is the only working medium in the circulation channel. Further, the heat exchange loop system 130 passing through the containment 110 is served as the heat removal channel, and can be adjusted depending on the temperal:ure of the working medium and the heat energy in the containment 110 thereby cooling down the containment 110 to the temperature below the design limiting temperature. While the configuration of the water tank assists in quickly removing the residual heat from the cont2inment 110 at the early stage of accident. After the water in the water tank 120 is evaporated completely, the part of the heat exchange loop system 130 that is located in the water tank 120 is exposed to the air and then the air is heated to move up along the upward channel 128, to form the organized natural air convection. In this way, the residual heat in the containment 110 is finally emitted into the atmospheric environment. Thus, the containment 110 still can be cooled for a long time by means of the air cooling mode in a condition that the cooling water in the water tank 120 is evaporated to dryness. The present system can be operated passively and safely without turning on some valves and without any other assistant equipment, thus the structure is simple and the weight is light which is convenient for maintenance.

[0060J While the invention has been described in connection with what are presently considered to be the most practical and preferred embodiments, it is to be understood that the invention is not to be limited to the disclosed embodiments, but on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the invention.

Claims

WHAT IS CLAIMED IS: 1. A passive concrete contaimnent cooling system, adapted to remove heat from a containment, comprising: a waler tank adapted for being configured on a top of the containment, and the water tank being divided into a water cooling downward channel, an air cooling doiiward channel and an upward channel which are communicated with one another, the air cooling downward than nd and the upward channel communicated with the atmosphere respectively; and at least one heat exchange loop system adapted for hermetically running through the containment, a part of the heat exchange loop system being placed in the upward channel while the rest adapted for being located in the contamrnent.
2. The passive concrete containment cooling system according to claim I, wherein the heat exchange ioop system comprises a condenser placed in the upward channel.
3. The passive concrete containment cooling system according to claim 2, wherein the heat exchange loop system further comprises a heat exchanger adapted for being configured in the containment, an upward pipe and a downward pipe, the upward pipe is adapled for hermetically running through the containment and has two e:nds communicated with upper ends of the heal exchanger and Le condenser respectively, and I-he downward pipe is adapted for hermetically running through the containment and has two ends communicated with lower ends of the heat exchanger and the condenser respectively.
4. The passive concrete containment cooling system according to claim I, wherein the water tank is provided with a bottom wall as well as an internal wall and an external wall that are connected to and spaced with the bottom wall, and the internal wail, the external wall and die bottom wail are enclosed to form a receiving space.
5. The passive concrete contaimmcnt cooling system according to claim 4, wherein a first bafile and a second baffle separated from each other are vertically configured in the recelving space of the water tank, a gap is formed between a lower end of the first baffle and the bottom vall and between a lower end of the second baffle and the bottom wall respectively, the upward channel is foniied between the first baffle and the second baffle, the water cooling downward channel is fornied between the first baffle and the internal waiL amid the air cooling downward channel is formed between the second baffle and the external wall.
6. The passive concrete containment cooling system according to claim 5, wherein the water tank is further provided vitli a top plate, both the internal wall and an upper end of the first baffle are connected to the top plate, an opening is formed between an upper end of the second baffle and the top plate whereby the upward channel is communicated with the atmosphere.
7. The passive concrete contaimncnt cooling system according to claim 6, wherein a gap is formed between the external wall and the top plate whereby the air coohng downward channel is corn niunicated with tile atmosphere.
8. The passive concrete containment cooling system according to claim 4, wherein the water tank is in a circular structure,
9. The passive concrete containment cooling system according to claim 1, wherein the water tank is separated into multiple independent water pools each of which is provided with the water cooling downward channel, the air cooling downward channel, the upward channel and the heat exchange ioop system.
1O.The passive concrete containment cooling system according to claim 1, wherein the heat exchange loop system is a heat pump system.
11.The passive concrete containment cooling system according to claim 1, fiuther comprising a condensate recovery system adapted for being configured in the containment and communicated with a reactor pit in the containment.
1 2.The passive concrete containment cooling system according to claim 11, wherein the condensate recovery system comprises a first condensate collector adapted for being arranged on an inner wall of the containment and communicated with the reactor pit, and the location of the first condensate collector is higher than that of the reactor pit.liThe passive concrete containment cooling system according to claim 12, wherein the first condensate collector is communicated with the reactor pit via a first valve.l4.The passive concrete containment cooling system according to claim 12, the first condensate collector is in a groove structure and has a side va1l resting on the inner wall of the containment.1 5.The passive concrete containment cooling system according to claim Ii, wherein the condensate recovery system further comprises a second condensate collector adapted for being: configured in the containment, located under the heat exchange loop system and communicated with the reactor pit, and die location of the second condensate collector is higher than that of the reactor pit.1 6.The passive concrete containment cooling system according to claim 15, wherein the second condensate collector is communicated with the reactor pit via a second valve.1 7.The passive concrete containment cooling system according to claim 1 5, wherein the second condensate collector is in a V-shaped structure.